Though Apple device-specific battery cases now receive disproportionate attention, device-agnostic rechargeable battery packs have been popular alternatives for years. Just Mobile's Gum series has been a leader ever since the original Gum and Gum Pro debuted in 2008. Since then, there have been two Gum Plussequels, two considerably larger Gum Maxversions, and even a complete refresh of the basic Gum. Today, we're reviewing the latest model Gum++ ($90, aka Gum Double Plus), as well as a brand-new rival from SwitchEasy called Tanks ($70). Despite their considerable price differences, Gum++ and Tanks are substantially similar in performance, differentiated more by industrial designs and under-the-hood tweaks than major features that will matter to most users.

The rechargeable batteries inside Gum++ and Tanks are both 6000mAh cells, middle of the road by today’s standards: battery cases typically start at 1500 to 1800mAh, roughly enough to recharge an iPod, while huge standalone batteries tap out at around 12000mAh, or enough to nearly refuel current full-sized iPads. Just Mobile and SwitchEasy therefore picked a capacity that iPod and iPhone users will find ideal—enough for at least two full iPhone recharges and three or more complete iPod recharges. iPad recharging will vary based on the iPad model. Gum++ recharged a completely dead iPad mini to the 91% level, and Tanks hit 89% in one iPad mini test, then 96% in another, for an average of roughly 93%. Similarly, Gum++ restored 33% power to a fourth-generation iPad, enough for around three hours of extra run time. Both batteries’ results were a bit higher than the average we’ve seen for 6000mAh cells, but not the very highest on our charts.

Putting price aside, two key factors differentiate Gum++ from Tanks, starting with aesthetics. Resembling a piece of luggage thanks to long ribs and extended corners, the roughly 3.1” by 2.3” by 0.9” Gum++ is the first Just Mobile battery since the original Gum and Gum Pro to be made fully from plastic rather than mixing aluminum and plastic. The new design led to a wide range of “like,” “neutral,” and “don’t like” responses from our editors, though this particular writer found the silver, white, or black shells to be almost as appealing as the prior Gum Plus models, and definitively superior to the family’s earliest all-plastic designs. By contrast, the scuba tank-shaped Tanks houses its two battery cells inside a housing that’s around 0.2” taller and narrower than Gum++, with a nearly 0.5” thicker center. Users can choose from white or black colors, each primarily glossy with matte hard rubber bumpers on the edges and bottom, plus a matching detachable rubber double-port cover. SwitchEasy’s design is undeniably cool and unique in the Apple battery world, but will bulge more in a pocket than Gum++, and we can easily see the port cover getting lost or misplaced. The choice of which will better fit your usage scenarios is a purely personal one.

The other key difference between Gum++ and Tanks is charging speed. For a first-generation SwitchEasy battery, Tanks is nicely designed, using a four-segment light bar and power indicator/power switch button to depict its remaining energy. It can be refueled using an included micro-USB to USB cable at a peak speed of 1.6 Amps—that’s notably faster than many USB batteries, assuming you use a fairly recent Mac or self-supplied iPad-ready power adapter to charge it. In the outbound direction, Tanks supplies iOS devices with power at a top speed of 2.1 Amps, matching the peak speeds of iPods, iPhones, iPad minis, and non-Retina full-sized iPads.

By comparison, Gum++ runs at even faster 2.5-Amp top speeds in both directions, making it capable of refueling itself and Retina iPads in a shorter period of time than Tanks—for instance, Gum++‘s 33% recharge of a fourth-generation iPad took only 1 hour and 45 minutes. Since Gum++‘s 6000mAh capacity isn’t ideally suited for the last two full-sized iPads, its ability to match their peak speeds arguably isn’t critical, however, very few batteries have 2.5-Amp support in either direction, let alone both. Just Mobile also deserves praise for evolving the 4400mAh, 0.5-Amp Gum Pro to the 6000mAh, 2.5-Amp Gum Plus in less than five years while making only the most modest changes in size; the unit’s persistent five yellow power indicator lights and slightly recessed power button similarly benefit from years of tiny tweaks to improve their usability.

The only serious problem here is the pricing, which is on the high side for both batteries, but particularly high for Gum++ given what’s in the package. At $90, Gum++ is only $20 less expensive than Just Mobile’s recently-discontinued Gum Max, which included 40% higher battery capacity in an aluminum shell, plus a carrying bag and Apple device charging cable that aren’t packed in here. Only Gum++‘s compact size offers a definitive advantage over the considerably larger Max, but you give up a lot of power and frills for the lower price. By comparison, SwitchEasy’s Tanks delivers a highly similar charging experience for most Apple devices at a $20 lower price tag, with the same single-cable pack-in and plasticky shell. It’s not fancy, but it’s not priced at a premium accessory price—$70 is less expensive than almost any iPhone battery case around, and you get more than twice the power capacity, with broader device compatibility. Of these two options, we’d go with Tanks for use with iPods, iPhones, and iPad minis, and suggest Gum++ primarily for Retina iPad users. They’re both good batteries, but thanks to more aggressive pricing, Tanks has the edge, meriting our B+ rating and strong general recommendation to Gum++‘s flat B and general recommendation.

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Editors' Note: iLounge only reviews products in "final" form, but many companies now change their offerings - sometimes several times - after our reviews have been published.
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